Life Before Model Systems: General Zoology at August Weismann's Institute 1

Transcription

1 AMER. ZOOL., 7: (1997) Life Before Model Systems: Geeral Zoology at August Weisma's Istitute 1 FREDERICK B. CHURCHILL Departmet of the History ad Philosophy of Sciece, Idiaa Uiversity, Bloomigto, Idiaa 474 SYNOPSIS. With the curret iterest i ad criticism of Model Systems Research i mid, I review some of the details of a research program at the tur of the cetury. I preset data about career trajectories of the degree recipiets i August Weisma's Istitute of Zoology, i Freiburg i/br., Germay. I eumerate the orgaisms they use i their research ad provide some discussio about the level of aalysis performed by certai studets boud for academic careers. I coclude that betwee 188 ad 1912 diversity prevailed i career objectives, research projects, orgaisms ivestigated ad levels of aalysis. This was the diversity of a Geeral Zoology suited to Weisma's primary iterests i evolutio ad the cotemporary expectatios of academic zoology. This Geeral Zoology cotrasts with the orgaism specific research prevalet at the same istitute directed by Has Spema betwee 1918 ad 191. I closig I propose a sequece of historical stages which chaged the Geeral Zoology at the begiig of the curret cetury ito Model Systems Research at the ed. Durig the past cetury biology has made eormous strides by i-depth studies of a few orgaisms. I popular imagiatio the white mouse, the fruit fly, the guiea pig, field cor ad ow the zebrafish have bee parters ad martyrs to our advaces. More sophisticated i their perspective of evets, professioal biologists also eumerate Neurospora, E. coli, Xeopus, Arabadopsis ad scores of other orgaisms, which serve as research subjects for the workig out of fuctioal, geetic ad developmetal problems. The degree to which biologists ca geeralize their research results beyod the exemplary species plucked from ature's multitude has always bee a cotroversial matter, but i this age of high-tech biology ad high cash commitmets to medical research it is icreasigly temptig to cofer o exemplars of give fuctios the status of uiversal models. The claim beig made through such a tactic is a cogitive oe, that is, that a chose species, or a domesticated, stadardized sub-populatio of that species, 1 From the Symposium Forces i Developmetal Biology Research: The ad Now preseted at the Aual Meetig of the Society for Comparative ad Itegrative Biology, 26- December 199, at Washigto, D.C. may serve as a microcosm of a importat segmet of the orgaic macrocosm. The successful coferral of model system status, however, has ievitable repercussios o both the traiig ad research sides of a biology program. Both the cogitive ad istitutioal roles of what is ow referred to as model systems biology, form the focus of a umber of recet discussios. Microbiologist Howard Gest has questioed the "Rosetta Stoe" metality that has drive may biologists to espouse model systems (Gest, 199). He remids us of ad edorses what Has Krebs oce called the "[August] Krogh priciple," amed after the famous Daish physiologist, who wrote that "For a large umber of problems there will be some aimal of choice or a few such aimals o which it ca be most coveietly studied" (Krebs, 197; Krogh, 1929, p. 247). Krogh thereby implied that coveiece, i a broad sese, ad specific problem solvig, ot a presumptive geeral model, had ad should guide the choice of a orgaism i research (Gest, 199). Developmetal biologist Jessica Bolker has provided a thoughtful aalysis of some of the shortcomigs of a model systems approach: the uavoidable biases i the orgaism selec- 26

2 GENERAL ZOOLOGY 261 tio process, the cofusio of experimetal coveiece for uiversality, ad a frequet disregard of phylogeetic reality are amog the dagers she discusses (Bolker, 199). Historia Larry Holmes, who examied Krogh's origial ivocatio withi a historical sketch of the use of the frog as a commo research orgaism, put the questio most succictly whe he observed that "Throughout the history of biological ivestigatio, however, the questio of how far oe ca exted coclusios draw from particular orgaisms to other orgaisms (ofte most crucially to humas) has remaied problematic" (Holmes, 199, p. 1; see also Buria, 199). My paper represets the flip side of these discussios. I propose to examie a zoological research program at the ed of the ieteeth cetury, i which there was o cosideratio of model systems, i part because that claim would have bee atithetical to the very essece of the program. I do ot wish to imply that the zoology of the twety-first cetury should emulate the past, but a historical excursio ca sometimes provide a les through which we ca more critically examie a cotemporary issue. First, I should say some geeral words about my iterests. For a umber of years the late Professor Helmut Risler ad I have bee examiig i some detail the zoological istitute i Freiburg, which betwee 187 ad 1912 was directed by August Weisma. By readig letters ad collectig promotio Gutachte, we have assembled a good picture of this istitutio where research claims were beig pursued, lives shaped, aspiratios filled or i some cases, ot filled. Here I propose to examie whether or ot research at that istitute represeted a uified program, ad with these cosideratios Weisma's ow research trajectory is relevat for but should ot be equated with the istitute. After all, there were other Dozete, ad a umber of assistat professors who ispired studets, developed techiques, ad helped frame ad aswer scietific questios. Noetheless, Weisma set the itellectual toe ad, as oe of the most distiguished evolutioary biologists i tur-of-the-cetury Germay, he determied the ageda for the istitute as a whole. The zoology pursued was Weisma's zoology ad may of the idividual research projects were suggested by him. FREIBURG ZOOLOGICAL INSTITUTE Weisma took charge of the "zoological istitute" ad its collectios i At that time, it was affiliated with the medical faculty ad was little more tha a istitute i ame. It provided the medical faculty with courses i comparative aatomy ad embryology, i parasitology ad laboratory traiig i zoology (zootomisches Practicum). I 187 the Lehrstuhl for zoology ad the istitute were trasferred to the Philosophical Faculty, ad oly the did Weisma begi holdig his famous lecture course o the theory of evolutio, which evetuated i his Vortrdge der Descedeztheorie of 192 (Weisma, 192; Nauk, 194, 196). For te years after the trasfer to the Philosophical Faculty, Weisma's physical setup chaged little; that is, he ad his studets worked i two cramped rooms o the fourth floor of the "Old Uiversity." Oly after the Uiversity of Muich attempted to hire him away i 1884, could he fially extract from the cultural miistry a ew twostory buildig. This opeed its doors two years later whe Weisma was at the height of his creative powers. Three years later the state fiished the eighborig sigle-storied buildig to house the zoological collectios, ad i 197 it completed a 24- seat lecture hall, which joied the two older buildigs. By the time of Weisma's iaugural lecture of the witer semester of 197/198, studet demad required the uiversity istall a additioal 1 seats (Kohler, 197). Durig Weisma's forty-five year teure as director of the zoological istitute, its fuctio had chaged from providig pedagogical services for the medical school to a zoological research istitute first i the Philosophical Faculty, ad later i the Faculty of Natural Scieces ad Mathematics. Similar growth patters occurred with other zoological istitutes i Wilhelmie Germay, most of which were liberatig themselves from the straglehold of huma aatomy (Nyhart, 199). The patter i Frei-

3 262 FREDERICK B. CHURCHILL TABLE 1. Frequecy of degrees grated to core studets i five year icremets, the aual average of all degrees durig those icremets, ad the percetage chage. Five year icremets Total: Number of degrees Average of % chage from Ph.D. & Hab both per year precedig period * * Six of the sixty-oe core studets received their doctorates ad habilitated at the Freiburg Istitute, brigig the total umber of degrees to sixty-seve. burg was particularly dramatic, for it occurred with a expasio ad elevatio i prestige of the uiversity itself, from a margial to oe of the most promiet secod tier uiversities i the Germa empire. By the first decade of the twetieth cetury, the Uiversity i Freiburg had achieved a par with the Uiversity at Heidelberg, the other Uiversity i the State of Bade (Riese, 1977). This overall patter idicates the degree to which zoological istitutes i Germay i geeral ad Freiburg i particular were situatig themselves ot oly to produce kowledge ad service the zoological iterests of the uiversity, but also to trai Doctorate ad Dozete. It is to these latter I wish to tur to preset certai demographic profiles ad to suggest how these might speak to the curret iterest i model systems. Two PROFILES OF CORE STUDENTS I our survey of uiversity documets ad dissertatios betwee 188 ad 1912, we have bee able to establish a core of 61 Doctorate ad Dozete i zoology, who collectively provide a group that I will call the "core degree studets" at the istitute. The followig two tables preset useful demographic profiles of these ad other studets at Weisma's istitute. Table 1 idicates the frequece of degrees grated to core studets, chroologically ordered. The geeral tred ad the short term decrease i core studets i TABLE 2. Variety of career choices of all degree recipiets, icludig core studets at the Zoological Istitute ad Ph.D. recipiets from the Aatomy Istitute. % of total Career choices Number of graduates umber of career choices Uiversity zool/aat Uiversity other 7 9. Explorer aturalist 7 9. Museum employmet Professioal zoologist Secodary teacher Died i WWI 1 1. Ukow Total of career choices 7* 1. * Sice a few of the studets had multiple careers, there are more total career choices tha degree recipiets parallels the erollmet curve i the philosophical faculty ad at most Germa uiversities. Durig the period of dramatic rise betwee 19 ad 199 there was a icrease i overall erollmet at Freiburg of 27.6% (Riese, 1977). Tracig the post-graduate careers of may of the PhD studets is a difficult ad time cosumig udertakig (Table 2). Sice there is o systematic way of idetifyig either secodary school teachers or early deaths, particularly i World War I, this might explai why so may former studets (28%) have disappeared from sight. This group of missig studets, so to speak, is ulikely to iclude may uiversity or techical high school (Techische Hochschule) academics. Of those studets whose career path ca be positively idetified, a surprisig umber of doctoral studets (22.7%) pursued academic careers, either by habilitatig i zoology i Freiburg, by movig to aother zoology or aatomical research istitute i Germay i order to habilitate, or by eterig academic systems outside of Germay. A smaller umber (9.%) etered other academic fields, such as geology or physics. The third largest group (14.7%) cosisted of o-academic, professioal zoologists. I iclude i this group idividuals who wrote a occasioal zoological paper, but who did ot seem to have a academic affiliatio with a traditioal uiversity or techical uiversity. Also icluded i this group are

4 GENERAL ZOOLOGY 26 former studets who became ivolved i govermetal or idustrial research. Museums offered a importat source of employmet (12%) for studets with the Ph.D. i Zoology. Frequetly overlappig with museum work as a professio was a career trajectory that bega with field collectig ad exploratio overseas, ofte i the ew Germa coloies (9.%). RESEARCH ORGANISMS AT THE INSTITUTE It is my belief that these studet profiles (chroological frequecy ad career trajectories) provide some perspective o, though ot ecessarily a explaatio for, the varied patter of research projects pursued at the isitute. To begi with, the array of orgaisms that studets ivestigated strikes the late twetieth cetury eye as astoudig. Three classes of vertebrates, oe class of echioderms, arthropods of all descriptios with over differet species ivolved, ad a scatterig of polychaetes, ematodes, flatworms, coeleterates, ad spoges all came through the doors; may were kept for study over periods of moths, maybe for a few years, ad sometimes through may geeratios util the studet completed his or her dissertatio. This, of course, meat aquaria, cages, cold chests, ad rearig pes. It ultimately required coveietly accessible collectio storage. From this it seems self-evidet that Weisma ad his studets operated withi the cotext of a geeral zoology cocered with morphological ad phylogeetic questios that depeded o cross-type comparisos. Weisma's ow research ad writigs almost always carried the same thrust. Comparative aatomy, embryology, ad cytology were the essece of most research projects. If we look more closely at the array of orgaisms studied, we ote that eight dissertatios dealt with vertebrates, but oly two of these were doe by core zoology studets. The other six dissertatios o vertebrates were writte by foreig studets workig i the aatomy istitute directed by Weisma's brother-i-law, Robert Wiedersheim. Istead of receivig M.D.S however, they chose to collect Ph.D.s o the basis of Weisma's recommedatio to the Philosophical Faculty. This cotrast implies a divisio of labor i Freiburg betwee the two istitutes: vertebrates i aatomy through the medical faculty ad ivertebrates i zoology through the philosophical faculty. Aother observatio o the array of ivertebrates ivestigated at the istitute is worth reportig. Forty-oe of the dissertatios ad three of the seve Habilitatiosschrifte cocered questios havig to do with isects or crustaceas geerally, but ot always, i a comparative mode. This makes sese for a umber of reasos. Weisma carried out extesive comparative studies ad experimets o butterflies; his reowed butterfly collectio ad his temperature iduced variatio experimets o lepidopteras were the direct results of questios he had about seasoal ad sexual dimorphism, rage of variatios, ad mimicry. Although these questios had strog developmetal ad hereditary implicatios, they were ultimately desiged with Weisma's ow evolutioary argumets i mid. Weisma had also extesively studied crustaceas, particularly the cladoceras ad copepods of the Bodesee, ad his ad Chiyomatsu Ischikawa's microscopic studies of reductio divisio were doe largely o this group of arthropods. For the studets i the istitute the techiques of preservatio ad study of isects ad the collectios were largely i place for their ow research problems. Despite this cocetratio o isects ad crustaceas o oe would have spoke of ay group, let aloe a sigle species, as a model system. Of the 7 differet research projects oly 2 were focused o sigle species. Weisma was costatly askig, ad forcig his studets to ask, about the cross-taxo geerality of ay pheomeo he or they might be ivestigatig. Oe may poit to oe exceptio to this patter ad that is the work doe by Wilhelm Paulcke ad Alexader Petrukewitsch o the domesticated hoey bee, Apis mellifer (Paulcke, 19; Petrukewitsch, 191, 192). The work was strogly ecouraged by Weisma who over a te year period was led ito a exteded reexamiatio of the productio of droes by the

5 264 FREDERICK B. CHURCHILL Darmstadt teacher, publisher ad beekeeper Ferdiad Dickel (Churchill, 1974). The latter had claimed to have repudiated the log accepted belief, first put forward by Johaes Dzierzo i the 184s, that droes were the products of partheogeesis. The istitute's studies supported Dzierzo's claim. If Dickel had bee correct, ad iitially Weisma hoped he was, the studies would have let support to a developmetal rather tha a particulate explaatio of sex determiatio. (I Weismaia termiology this would have idicated the germial selectio of all sex "Determiats" rather tha the actio of a sigle "Determiat.") Whatever the outcome, we fid i this affair more tha oe studet pursuig a well delimited problem with the same orgaism. Much came out of this focused research. Ivestigators from other istitutes cotributed briefly to the scietific exchage; the Dzierzo theory was recofirmed usig the most up-to-date histological techiques; Petrukewitsch improved a fixative that became a stadard reaget i microscopy, ad Weisma was deied a possible demostratio of a developmetal determiatio of sex. It was a short lived episode, ad oe ca hardly speak of the hoey bee becomig a model system. No oe systematically kept bees at the zoological istitute. I the terms of Krogh's priciple, hoey bees were the coveiet orgaism for the study of the productio of droes. Today we might cosider the species as a example of sex determiatio i social hymeopteras, but this is a modest claim compared with those associated with model systems. DIVERSITY OF RESEARCH QUESTIONS Overall, the dissertatios ad Habilitatiosschrifte recommeded by Weisma posed a wide diversity of research questios. For a cetury preoccupied with embryological research it is ot surprisig to fid that over forty-four or 61% of the sevety-three separate research projects, i.e., sixty-seve projects by core studets ad six by studets i aatomy, had a strog developmetal focus. Despite this commoality their idividual research questios raged from descriptive studies of developmet to studies about reproductio, sexual determiatio, life cycles, ad regeeratio. Fiftee of these developmetal ivestigatios examied i oe way or aother the productio of gametes, a subject that was of great iterest to Weisma. Oly eight of the developmetal projects assumed a recapitulatio of specific traits from acestral forms, ad oe that I have yet read ivoked the biogeetic law. A relatioship betwee otogey ad phylogey was always assumed, but Haeckel's fudametal priciple did ot ispire, let aloe shape, the research program i Freiburg. Fiftee (<21%) of the projects were aatomical i focus, but as with the developmetal projects there was o sigle theme. Seve of them were cofied to aatomical studies of sigle orgaisms (four of these beig doe at the aatomical istitute); five of the fiftee had comparative aatomical themes ad three were what I ca oly describe as fuctioal aatomy, i.e., makig coclusios about fuctio by examiig structure ad performig simple ad limited experimets. Five other projects (<7%) were focused o evolutio by addressig questios about biogeographical distributio, covergece, ad phylogeetic lieages of adult structures. Four more (<6%) dealt primarily with taxoomic questios; oe (<2%) examied the comparative degeeratio of structures i related species; oe (<2%) ca oly be described as a experimetal study i heredity, ad the last two projects (<%), both dissertatios, were based o literature evaluatios i what I might describe as studies i philosophy of biology. It must be emphasized that may of the dissertatios icorporated more tha oe of these focuses, ad it was ot ucommo for a dissertatio to examie developmet, adult aatomy, fuctios of sigle structures ad phylogeetic relatioships of several species at the same time. Geerally, however, it was ot difficult to idetify a primary focus. LEVELS OF ANALYSIS Aother oteworthy feature of these research projects is the rage i the level of aalysis. It must be emphasized, however, that may of these moographs switch from oe level to aother, but agai it is geer-

6 GENERAL ZOOLOGY 26 TABLE. Frequecy of various levels of aalysis of sixty zoology dissertatios ad Habilitatiosschrifte. Level Literature aalysis Orgaism Gross aatomical Tissues ad germ layers Cellular Nucleus ad chromosomes Total: Number % of total ally ot difficult to ascertai a priciple focus. Of sixty moographs that I have bee able to examie with this questio i mid, I fid the distributio show i Table. This rage of levels agai suggests a diversity i research projects, which implies i tur a diversity of the istrumets ad techiques routiely used. It might be valuable to examie how this diversity chaged over time. It might also be iterestig to correlate the levels of aalysis with studets who took differet professioal tracks, for this might help us determie how dissertatio topics were assiged or sactioed ad the extet to which Weisma might have bee ivolved i career choices. Ufortuately, I caot address these latter two questios, but here are some prelimiary observatios arrived at by examiig the thirtee Germa academic boud zoologists (Table 4). Nothig i Table 4 will be surprisig, ad I am ot eve cofidet that the sample size is large eough to establish ay treds, but I will be brash eough to suggest three, which might be relevat to the questio of the emergece of model systems research: 1) academic boud zoologists teded durig this period to move to deeper levels of aalysis as they wet from the dissertatio to the Habilitatiosschrift; 2) the deeper levels of aalysis became more commo over time, ad ) oly two of the academic boud zoologists (Petrukewitsch ad Schleip) did their dissertatios ad Habilitatiosschrifte o the same orgaism, ad their research appeared toward the ed of our period. If these treds are real, ad a ituitive guess based o the reductioist tred of zoology would suggest they are, they might be explaied i a umber of, ot mutually exclusive, ways: 1) Research problems ad hece hirig patters, icreasigly favored deeper levels of aalysis. 2) Icreasigly refied equipmet ad techiques became more commoly available or stadard i the TABLE 4. Chages i the levels of aalysis over time ad from dissertatio to Habilitatiosschrift of fourtee Uiversity boud Germa zoologists. Name Gruber Ziegler Korschelt Fritze Haecker Spuler Woltereck Paulcke Giither Petruk. Schleip Strohl Demoll Kiih Year Level g r org tis gr tis gr tis Dissertatio Value" R/A" Year ? Habihtatiosschft * Values other tha are assiged to the level of aalysis: = work ot doe i Freiburg ad is ot icluded i the ruig average; 1 = focus o the whole orgaism (org); 2 = focus o the gross aatomical or orga level (gr); = focus o the tissues (tis); 4 = focus o cells (eel); = focus o the ucleus (). b R/A = Ruig Average. c As a protozoologist Griiber worked at both the level of the whole orgaism ad the ucleus simultaeously, givig his Habilitatiosschrift a value of or (1 + )/2. Level gr/ eel org eel Value R/A

7 266 FREDERICK B. CHURCHILL istitute over time. ) Weisma etrusted aalysis o the deeper levels to his better ad more advaced studets. It is worth otig that Weisma's ow research had a more complex chroological profile. Durig the thirty-four year period covered i Table 4, it moved i a erratic way with respect to the level of aalysis ad geerally i the opposite directio suggested i the table. Weisma completed his studies of germ cell migratios by 188; he performed, with the assistace of Ischikawa, polar body ad reductio divisio work i the mid 188s, ad by the 189s he was writig largely theoretical texts ad doig detailed research o mimicry ad iduced coloratio o the orgaism level. His research optios were ofte resposes to his recurrig retia problems, which kept him from pursuig exteded microscopic studies. CONCLUSIONS: MODEL SYSTEMS AND GENERAL ZOOLOGY What are the implicatios of these historical data for cotemporary discussios of model systems? First, I am struck by the repeated maifestatios of diversity i so may aspects of the operatio of the zoological istitute i Freiburg. There was i Weisma's day a diversity i the life trajectories of the studets, a eormous rage of research orgaisms, a multitude of differet research themes, ad a eve-haded attetio to may levels of aalysis, which i tur implied a diversity of techiques ad istrumets. May studets had very differet goals i research ad careers tha that which Weisma may have harbored for the very best. Their idividual desires were ecouraged ad accommodated withi the framework of a geeral zoology program. I suspect that may of these forms of diversity would be atithetical to the more focused research arisig from the exploitatio of a sigle orgaism ad a model systems ageda. Secod, I have oly hited at the relatioship betwee Weisma's ow research ad those of his studets, but I am cofidet that this was more complex tha the traditioal stereotype of a Geheimrat Professor parcellig out segmets of his research program to studets who simply did the meial tasks. The impressio of the research projects at Weisma's istitute emphasizes the past iterest i the variety of life's pheomea ad so idicates a collective cocer about all of the processes of evolutio, developmet, ad heredity. This breadth forced a rage i methods from taxoomy to experimetal breedig ad from biogeography to chromosomal studies. Third, a commo bod betwee Weisma's ad his studets' works, however, ca be see. Weisma's all-ecompassig germ plasm theory, which emerged i the early 188s ad was the achor of his research thereafter, ad his costat probig ito the complexities of the evolutioary process set a framework for all the research doe at the istitute. Evolutio theory i 19 called for a geeral zoology that exposed the studet to the great diversity i developmet, reproductio, morphology, ad geographical distributio of a large umber of orgaisms. May a dissertatio would deal with most of these dimesios to life; so the comparative approach was imperative. Fourth, Weisma's geeral zoology also mirrored the ature of the academic professio i Germay. To become a successful academic zoologist, that is, the possessor of a Lehrstuhl ad the director of a zoological istitute, a aspirig cadidate was compelled to establish his familiarity with a wide rage of orgaisms, themes ad approaches (Harwood, 199). Fifth, it is useful to compare, if oly i passig, Weisma's program with the zoology program pursued whe betwee 1918 ad 191 Has Spema became director of the same Freiburg istitute. Durig this period his studets wrote twety-four dissertatios ad five Habilitatiosschrifte (FaBler, 199). Of these oly four, or 1.7%, dealt with orgaisms other tha urodeles ad auras, ad the vast majority focused exclusively o the salamader Trito. Collectively these studies opeed up a picture of the process of iductio i early vertebrate developmet. Fially, if "model systems" is goig to be a useful expressio i biology, the his-

8 GENERAL ZOOLOGY 267 toria might cosider at least three stages i the rise of such a strategy: 1) the time whe huma ad material resources of a etire istitute become mobilized to ivestigate a specific problem i a sigle coveiet orgaism; 2) the time whe a orgaism becomes stadardized through domesticatio, i-breedig ad selectio; ad ) the time whe pressures develop for researchers to make cogitive claims about the uiversality of their chose orgaism. Sigificat historical efforts have bee made toward examiig the secod of these phases (Kohler, 1994; Clause, 199; Rader, 199). To uderstad better the trasformatio of the first of these phases, the historia might start with the secod decade of this cetury whe the geeratio of Spema, Morga, ad others istitutioalized the i-depth study of give orgaisms. I close by otig that whe i 1929 August Krogh wrote the passage that was later eshried ito the priciple bearig his ame, he explicitly recommeded that i order to fid the correct orgaism for a problem, "we [i.e., physiologists] must apply to the zoologists to fid them ad lay our hads o them" (Krogh, 1929, p. 247). He presumably was referrig to practitioers of the geeral zoology traditio so well exemplified i Weisma's istitute. Krogh ad his colleagues had eed to haste, however, because may zoologists, after wiig their idepedece from the medical faculties i the 187s ad '8s ad after establishig a thrivig traditio i geeral zoology for the ext forty years, were by the 192s headig dow the same model systems trail blazed by physiologists. ACKNOWLEDGMENTS This lecture has bee preseted uder variat titles at the Uiversity of Miesota ad Idiaa Uiversity, ad as a memorial tribute at Johaes Guteberg Uiversity at Maiz, where commets from listeers have helped sharpe the paper at may poits. The research has bee supported i part by a Germa-America Academic Cousel grat awarded to the author ad the late Helmut Risler of Maiz, Germay for their joit editorial project etitled August Weisma: Autobiographie, Dokumete, Gutachte ud Ausgewdhlte Briefe, 2 vols., to be published by Freiburg Uiversity Library Press. REFERENCES Iformatio about studets at the zoological istitute, their career trajectories, ad their dissertatios was gathered from umerous archival ad referece sources. The most importat were the Promotiosakte at the Uiversity Archives i Freiburg; Verzeichis der Behorde, hehrer, Astalte, Beamte ud Sludierede auf der Grossherzoglich Badische Uiversitdt Freiburg; Verzeichis der Deutsche Hochschulschrifte; Deutsches Biographische Archiv, ad the dissertatios ad Habilitatiosschrifte themselves. Bolker, J. A Model systems i developmetal biology. Bio Essays, 17:41-4. Buria, R. M How the choice of experimetal orgaism matters: epistemological reflectios o a aspect of biological practice, J. Hist. Bio., 199, 26:1-67. Churchill, F Weisma-Dickel correspodece o the partheogeesis of droes. Proc. X1I1 It. Cog. Hist. Sci., Sect. 9. Naouka, Moscow Clause, B. T The Wistar rat as a right choice: establishig mammalia stadards ad the ideal of a stadardized mammal, J. Hist. Bio. 26: FaBler, P. E Has Spema ( ). Experimetelle Forschug im Spaugsfeld vo Empirie ud Theorie. Ei Beitrag zur Geschichte der Etwicklugsphysiologie zu Begi des 2. Jahrhuderts. Iauguraldissertatio, Albert-Ludwigs-Uiversitat Freiburg i. Br. Gest, H Arabidopsis to zebrafish: a commetary o 'Rosetta Stoe' model systems i the biological scieces, Persp. Biol. Med., 7:77-8. Harwood, J Styles of Scietific Thought. The Germa Geetics Commuity Uiversity of Chicago Press, Chicago. Holmes, F. L The Old Martyr of Sciece: The Frog i Experimetal Physiology, J. Hist. Bio. 26: Kohler, O Die Zoologie a der Uiversitat Freiburg I. Br. I E Zetgraf (ed.), Aus der Geschichte der aturwissschafte a der Uiversitdt Freiburg I. Br., pp Kohler, R. E Lords of the fly. Drosophila geetics ad the experimetal life. Uiversity of Chicago Press, Chicago & Lodo. Krebs, H. A The August Krogh priciple: For may problems there is a aimal o which it ca be most coveietly studied. J. Exp. Zool. 194: Krogh, A The process of physiology. Am. J. Phys. 9: Nauck, E. T Zur Vorgeschichte der Naturwisseschaftlich-Mathematische Fakultdt der Albert-Ludwigs-Uiversitat Freiburg i. Br. Eberhard Albert, Freiburg. Nauck, E. T Die Privatdozete der Uiversitdt Freiburg i. Br. Eberhard Albert, Freiburg. Nyhart, L. K Biology takes form. Aimal mor-

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